.\"	$OpenBSD: SSL_CTX_set_info_callback.3,v 1.4 2018/03/27 17:35:50 schwarze Exp $
.\"	OpenSSL b97fdb57 Nov 11 09:33:09 2016 +0100
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.Dd $Mdocdate: March 27 2018 $
.Dt SSL_CTX_SET_INFO_CALLBACK 3
.Os
.Sh NAME
.Nm SSL_CTX_set_info_callback ,
.Nm SSL_CTX_get_info_callback ,
.Nm SSL_set_info_callback ,
.Nm SSL_get_info_callback
.Nd handle information callback for SSL connections
.Sh SYNOPSIS
.In openssl/ssl.h
.Ft void
.Fo SSL_CTX_set_info_callback
.Fa "SSL_CTX *ctx"
.Fa "void (*callback)(const SSL *ssl, int where, int ret)"
.Fc
.Ft void
.Fo "(*SSL_CTX_get_info_callback(const SSL_CTX *ctx))"
.Fa "const SSL *ssl"
.Fa "int where"
.Fa "int ret"
.Fc
.Ft void
.Fo SSL_set_info_callback
.Fa "SSL *ssl"
.Fa "void (*callback)(const SSL *ssl, int where, int ret)"
.Fc
.Ft void
.Fo "(*SSL_get_info_callback(const SSL *ssl))"
.Fa "const SSL *ssl"
.Fa "int where"
.Fa "int ret"
.Fc
.Sh DESCRIPTION
.Fn SSL_CTX_set_info_callback
sets the
.Fa callback
function that can be used to obtain state information for SSL objects created
from
.Fa ctx
during connection setup and use.
The setting for
.Fa ctx
is overridden from the setting for a specific SSL object, if specified.
When
.Fa callback
is
.Dv NULL ,
no callback function is used.
.Pp
.Fn SSL_set_info_callback
sets the
.Fa callback
function that can be used to
obtain state information for
.Fa ssl
during connection setup and use.
When
.Fa callback
is
.Dv NULL ,
the callback setting currently valid for
.Fa ctx
is used.
.Pp
.Fn SSL_CTX_get_info_callback
returns a pointer to the currently set information callback function for
.Fa ctx .
.Pp
.Fn SSL_get_info_callback
returns a pointer to the currently set information callback function for
.Fa ssl .
.Pp
When setting up a connection and during use,
it is possible to obtain state information from the SSL/TLS engine.
When set, an information callback function is called whenever the state changes,
an alert appears, or an error occurs.
.Pp
The callback function is called as
.Fn callback "SSL *ssl" "int where" "int ret" .
The
.Fa where
argument specifies information about where (in which context)
the callback function was called.
If
.Fa ret
is 0, an error condition occurred.
If an alert is handled,
.Dv SSL_CB_ALERT
is set and
.Fa ret
specifies the alert information.
.Pp
.Fa where
is a bitmask made up of the following bits:
.Bl -tag -width Ds
.It Dv SSL_CB_LOOP
Callback has been called to indicate state change inside a loop.
.It Dv SSL_CB_EXIT
Callback has been called to indicate error exit of a handshake function.
(May be soft error with retry option for non-blocking setups.)
.It Dv SSL_CB_READ
Callback has been called during read operation.
.It Dv SSL_CB_WRITE
Callback has been called during write operation.
.It Dv SSL_CB_ALERT
Callback has been called due to an alert being sent or received.
.It Dv SSL_CB_READ_ALERT
.It Dv SSL_CB_WRITE_ALERT
.It Dv SSL_CB_ACCEPT_LOOP
.It Dv SSL_CB_ACCEPT_EXIT
.It Dv SSL_CB_CONNECT_LOOP
.It Dv SSL_CB_CONNECT_EXIT
.It Dv SSL_CB_HANDSHAKE_START
Callback has been called because a new handshake is started.
.It Dv SSL_CB_HANDSHAKE_DONE
Callback has been called because a handshake is finished.
.El
.Pp
The current state information can be obtained using the
.Xr SSL_state_string 3
family of functions.
.Pp
The
.Fa ret
information can be evaluated using the
.Xr SSL_alert_type_string 3
family of functions.
.Sh RETURN VALUES
.Fn SSL_CTX_get_info_callback
and
.Fn SSL_get_info_callback
return a pointer to the current callback or
.Dv NULL
if none is set.
.Sh EXAMPLES
The following example callback function prints state strings,
information about alerts being handled and error messages to the
.Va bio_err
.Vt BIO .
.Bd -literal
void
apps_ssl_info_callback(SSL *s, int where, int ret)
{
	const char *str;
	int w;

	w = where & ~SSL_ST_MASK;

	if (w & SSL_ST_CONNECT)
		str = "SSL_connect";
	else if (w & SSL_ST_ACCEPT)
		str = "SSL_accept";
	else
		str = "undefined";

	if (where & SSL_CB_LOOP) {
		BIO_printf(bio_err, "%s:%s\en", str,
		    SSL_state_string_long(s));
	} else if (where & SSL_CB_ALERT) {
		str = (where & SSL_CB_READ) ? "read" : "write";
		BIO_printf(bio_err, "SSL3 alert %s:%s:%s\en", str,
			SSL_alert_type_string_long(ret),
			SSL_alert_desc_string_long(ret));
	} else if (where & SSL_CB_EXIT) {
		if (ret == 0)
			BIO_printf(bio_err, "%s:failed in %s\en",
				str, SSL_state_string_long(s));
		else if (ret < 0) {
			BIO_printf(bio_err, "%s:error in %s\en",
				str, SSL_state_string_long(s));
		}
	}
}
.Ed
.Sh SEE ALSO
.Xr ssl 3 ,
.Xr SSL_alert_type_string 3 ,
.Xr SSL_state_string 3
.Sh HISTORY
These functions first appeared in SSLeay 0.6.0
and have been available since
.Ox 2.4 .
